IMPROVEMENTS IN CARTON BLANKING UNITS

Abstract: A blanking unit (10, 10a) for striking carton blanks from a sheet(s) of material comprises a top blanking frame (12) and a bottom blanking frame (14). The top blanking frame is vertically reciprocal relative to the bottom blanking frame so as to strike blanks from the sheet material when interposed between the frames. The bottom frame is formed with cutting edges (W1-W6; R1, R2) to shear through the sheet and the top frame is furnished with a number of profile plates (P1-P4) one for each blank (B1-B4) to be struck. Each profile plate conforms substantially to the general profile of the blank it is to strike and is adjustable in relation to that blank and relative to the remainder of the sheet.

Description: IMPROVEMENTS IN CARTON BLANKING UNITS This invention relates to a carton blanking unit for blanking paperboard blanks and more particularly is concerned with the top blanking frame of such a unit which comprises cooperating top and bottom blanking frames. Blanking units of the type with which the present invention is concerned comprise a static bottom frame and a top frame vertically reciprocal relative to the bottom frame. In use a sheet of paperboard or other material is fed between the top and bottom blanking frames when the top frame is in a raised position and while the sheet is resident between the two frames and supported by the bottom frame, the top frame is lowered and, by engagement with the sheet and cooperation with the bottom frame the sheet is sheared to produce a plurality of blanks. This process is cyclic and the blanking unit produces a stack of carton blanks below the bottom frame which at some appropriate time is removed so that another stack can be built up. Typically the unit operates at a speed of 5000 - 8000 sheets per hour. The sheet which is to be blanked normally is scored and/or nicked in certain locations to form frangible boundaries which facilitate the production of carton blanks from the sheet. To this end, the bottom frame of the unit comprises a number of cutting edges. In some arrangements where the profiles of the blanks to be produced is (say) rectilinear, these cutting edges may comprise a series of transverse and longitudinal cutting wires stretched taught across frame side and end members. When the top frame is brought down to cooperate with the bottom frame, blanking profiles provided by the top frame engage the sheet between the frames and force the sheet through the plane containing the cutting wires so that the wires shear through the sheet along the frangible boundaries to produce the requisite blanks. Further downward movement of the top frame which puts the blanking profiles further still beyond the plane containing the wires cause the blanks to be stacked atop a pallet or an existing array of blanks created by the immediately preceding stroke of the top frame. In other arrangements, where, more complex blank profiles are required, the bottom frame cutting edges are provided, at least in part, by cutting blades which are shaped to cause the necessary separation of the boundaries of the sheet which define each carton blank. In known blanking units, the top frame blanking profiles comprise a multiplicity of adjustable arms which are secured to support bars of the top frame and arranged to act on an area of a sheet to be blanked which area defines a blank to be produced. The adjustable arms are arranged to impact on that sheet area evenly. In order to achieve this numerous such arms are required and the setting-up or make-ready time expended is considerable and the task laborious. One attempt to simplify the arrangement in which a multiplicity of arms is provided involves the use of a single blanking top plate profile approximating the size of the sheet to be blanked and which has a plurality of integral blank profile zones to impact on those areas of the sheet which are to become blanks. Although make ready-time in respect of this arrangement has been an improvement over the multi-arm structure, it was relatively non-adjustable or rather did not lend itself at all well for insitu adjustment. The present invention seeks to achieve the advantages of the known arrangements while avoiding the disadvantage of non-adjustability referred to above. The invention provides a blanking unit for striking carton blanks from a sheet of material comprises a first and second blanking frames in which the first blanking frame is reciprocal relative to the second blanking frame for cooperation therewith so as to strike blanks from a sheet of material interposed between said frames, wherein said first frame is formed with cutting edges to shear through said sheet and said second of said frames is furnished with a profile plate for each blank to be struck from said sheet, each profile plate conforming substantially to the general profile of the blank it is to strike and being adjustable in relation to that blank and relative to the remainder of said sheet. According to a feature of the invention, said first frame may be the bottom frame of the unit and said second frame may be the top frame of the unit, the top frame being vertically reciprocal relative to the bottom frame. An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a schematic perspective view of a top frame of a blanking unit; a paperboard sheet to be blanked; and a bottom frame of the unit shown in their relative operative positions; Figure 2 is a schematic perspective view of the paperboard sheet of Figure 1, the bottom frame of Figure 1 and a stack of carton blanks formed by the blanking operation; and Figure 3 is a schematic plan view of a top frame of a blanking unit, incorporating different blanking profile plates to those shown in the top frame in Figure 1, shown superimposed upon a paperboard sheet to be blanked and bottom frame respectively. Referring first to Figures 1 and 2 of the drawings a blanking unit 10 comprises a top frame 12 and a bottom frame 14 of which the top frame is vertically reciprocal, as shown by arrows R, relative to the bottom frame to strike blanks B1-B8 from paperboard sheet 5. In use the paperboard sheet 5 is fed between the frames, to be supported atop the bottom frame, in the direction of arrow F. The top frame is of generally rectangular form having main longitudinal and transverse frame numbers 16,18 respectively, and intermediate transverse members 20-26, respectively. Transverse frame member 18 is the leading or grip edge of the frame. Intermediate transverse members 20,22 carry a series of blank profile plates Pl- P7 and, likewise intermediate transverse members 24,26 carry a series of blank profile plates P2-P8. All the profile plates are individually slidably adjustable with respect to their associated transverse members by means of connecting legs "L" and can be locked in a set position by an adjustable locking screw "S". Some limited rotational movement about the locking screws is also possible. Longitudinal movement in the frame can be achieved by sliding the intermediate transverse members relative to longitudinal frame members 16 to which the intermediate transverse members are slidably attached. Thus each profile plate is adjustable in relation to the blank which it is to strike and with respect to other areas of the sheet. The profile plates are formed from 25mm plywood and include a closed cell sponge face on their lowermost sides. The cushioned lower face has been found to achieve a more positive stacking of the blanks and of course gives protection against damaging the printed surfaces of the blanks. The individual profile plates normally will be formed with at least one window to reduce the suction effect which can take place between the sheet 5 and the foamed face of the plates P1-P8. The window also gives improved visibility for inspection and insitu adjustment of the profile plates. Bottom frame 14 also is of generally rectangular form having main longitudinal and transverse frame members 28, 30 respectively and intermediate longitudinal and transverse cutting edges. In this particular construction the cutting edges comprises longitudinal cutting steels or wires W1-W5 and a transverse cutting steel or wire W6 arranged to shear the sheet 5 along the cut lines shown on the sheet as the profile plates pass through the spaces between adjacent cutting steels or wires. The wires are held taught across the frame by adjustable tensioning blocks "t". Referring now to Figure 3 of the drawings, a schematic plan view shows a blanking unit 10a in which the blanks to be struck are not rectilinear but have a more complex profile. In this arrangement four blanks B1-B4 are to be struck from a paperboard sheet. Profile plates P1-P4 (shown in stipling) which closely approximate the profiles of blanks to be struck are carried by the top frame 12 of the unit. The plates are all similar; thus, for example, plate PI is adjustably supported at the locations marked with a "+" by the intermediate frame members 24,26 of the top frame. The plates are each formed with a pair of apertures Al, A2 in order to relieve the suction effect between plate and blank and also to facilitate alignment of the individual plates. Generally, initial alignment of the profile blanks is carried out by locating the top frame over a tracing of the blanks layout and adjusting each profile plate so that it is accurately superposed upon a blank profile. The profile plates are sized 5mm to 25mm smaller all around their peripheries than the blanks B1-B4 to be produced. Spacers are included, as necessary, to set the profiles in the frame at the correct blanking height. Of course, the profile plates can be made to any desired shape or size to suit the carton blanks to be blanked from a sheet. The bottom frame 14 of the blanking unit is provided with longitudinal and transverse cutting edges formed by steel blades (20mm x 3mm) RI and R2 bevelled to provide a cutting edge and welded together. These cutting edges shear through the sheet to separate one blank area from an adjacent blank area. End El of the top frame is the so-called grip edge which comprises an end block at the frame member 18 formed from 18mm plywood having a free edge set lmm from the juxtaposed free edge of the sheet to be blanked. The grip edge carries a number of so-called jogging guides G which are fixed in the plywood to form guide faces for the leading edge of sheet. The term jogging which implies movement is adopted from an earlier arrangement in which guides to assist in stacking of blank were vibrated or "jogged". Other jogging guides G are located at the opposite end of the frame and along each of the sides of the frame. Further lateral guides "GL" formed from plywood are included at the back and sides of the frame. The jogging guides and lateral guides together locate the path of downward travel of the blanks to assist in more accurate and speedy stacking. Thus the cooperation between the top frame profile plates, passing through the spaces defined by the cutting rails and with the jogging and lateral guides produces a scissor action shearing force on the sheet to be blanked.

Claims: CLAIMS 1. A blanking unit for striking carton blanks from a sheet of material comprises a first and second blanking frames in which the first blanking frame is reciprocal relative to the second blanking frame for cooperation therewith so as to strike blanks from a sheet of material interposed between said frames, wherein said first frame is formed with cutting edges to shear through said sheet and said second of said frames is furnished with a profile plate for each blank to be struck from said sheet, each profile plate conforming substantially to the general profile of the blank it is to strike and being adjustable in relation to that blank and relative to the remainder of said sheet. 2. A blanking unit according to claim 1 wherein said first frame is the bottom frame of the unit and said second frame is the top frame of the unit, the top frame being vertically reciprocal relative to the bottom frame.

Inventors: PAUL MICHAEL, PAUL, MICHAEL
Applicants: MEAD CORP, PAUL MICHAEL, PAUL, MICHAEL, THE MEAD CORPORATION
Application year: 1994
Main classification: B26D1
IPC codes: B26D1, B26D7, B26F1